.one {
    position: relative;
    top: 0px;
    left: 0px;
    height: 360px;
    width: 100%;
    background: rgba(0,0,0,.77);
    background: radial-gradient( at center, rgba(0,0,0,.77), rgba(0,0,0,.77));
}

#particles-js {
    background-size: cover;
    background-position: 50% 50%;
    background-repeat: no-repeat;
    width: 100%;
    height: 360px;
    position: absolute;
    top: 0;
    left: 0;
}